This invention relates to a reservoir for containing reagent to be extracted and pipetted into multi-well test plates.
Multi-well test plates are well known in scientific areas, such as biotechnology, for allowing the detection and measurement of substances present in translucent liquid samples. Generally, this is accomplished by measuring the light absorbence characteristics of the sample through one or more spectroscopy procedures. Typically, a framework of test wells is opened at the top for receiving the liquid samples, and is closed with a transparent bottom for allowing light radiation penetration in a wavelength region necessary for a particular study. These studies, commonly referred to as assays, may include drug concentration assays, drug metabolite assays, enzyme activity assays, enzyme cofactor assays, fluorescent probe excitations or emissions, DNA spectral shifts or DNA and protein concentration measurements, as well as many other studies. The well plates typically consist of a plurality of individual wells configured so that an aliquot of a sample may be placed within each well. The wells are typically arranged in relatively close proximity in a matrix pattern, allowing samples to be studied individually or as a group. Common sizes for microplates include matrices having dimensions of 4xc3x976 (24 wells), 8xc3x9712 (96 wells), or 16xc3x9724 (384 wells), although larger well plates are also used that may include matrices of hundreds or even thousands of wells.
Prior to filling the well plates with reagent for carrying out the desired reaction and/or tests, a desired quantity of reagent is measured out into a reservoir. For example, if each well in a 96 well plate needs 1 milliliter of reagent for carrying out the measurement or reaction, a minimum of 96 milliliters of reagent is needed in the reservoir. A multiple head pipettor, in this case a 96 well pipettor head format, is used to extract the reagent for filling of the 96 wells. However, flat bottomed reservoirs or patterned bottoms with raised flat areas result in liquid hangup such that a portion of the liquid reagent is not positioned to be extracted into one of the heads of the multiple head pipettor. Thus, an additional amount of reagent is required to be added to the reservoir to account for the fact that some reagent will be wasted due to the design of the reservoir bottom. The reagents used for many of the assays are very expensive or precious, such that even small amounts of waste are unacceptable.
There is thus a need to provide a reagent reservoir and method for liquid reagent extraction that allows for full extraction of the liquid reagent therein by a multiple head pipettor.
The present invention provides a reagent reservoir with a patterned bottom that allows full extraction of a liquid reagent by a multiple head pipettor, and a method of using the reservoir. To this end, and in accordance with the present invention, the reservoir is provided having side walls and a bottom wall for containing the liquid reagent, wherein the bottom wall includes a plurality of recesses, each corresponding to a head of the multiple head pipettor. Each recess opens upwardly to receive the pipettor head, and includes a top edge, a bottom and surrounding side wall portions that angle outwardly from the recess bottom to the top edge. The recesses promote flow of the liquid reagent to the recess bottoms and prevent liquid hangup between recesses to eliminate waste of the liquid reagent. In one exemplary embodiment of the present invention, the surrounding side wall portions include four connected substantially triangular surfaces that angle outwardly from the recess bottom. In another exemplary embodiment of the present invention, the top edges between adjacent recesses meet at an angle to form a pointed peak. In using the reservoir, the interior of the reagent reservoir is filled with a desired volume of liquid reagent, the pipettor is positioned such that each pipettor head is aligned with a respective recess bottom, and the reagent is extracted. By virtue of the patterned bottom, substantially complete to full extraction of the reagent may be achieved.